The problem in these couplings is that the flushing medium (air or water) which flows through the cavity of the anchor pipes while drilling and the setting mass (for example cement mortar) which is pressed through the cavity of the anchor pipes toward their front end which is held in the borehole after completion of the borehole can escape in the area of known couplings. In this way losses of flushing media occur and in the case of setting mass with leaky couplings plugs of setting mass form which prevent complete filling of the borehole around the drill anchor.
A coupling of the initially mentioned type is known from DE-A-42 20 636. DE-A-4 220 636 shows a coupling of drill anchors with a sleeve with an inside thread and with two anchor pipes which bear an outside thread and which are screwed into the sleeve from opposing sides, essentially in the lengthwise middle of the sleeve there being an annular rib which projects to the inside, and the front surfaces of the ends of the anchor pipes held in the sleeves being located in the area of the annular rib and directly adjoining one another, the outside surfaces of the ends of the anchor pipes adjoining the inner end surface of the annular rib, forming a seal. In the coupling as claimed in DE-A-42 20 636 there are annular seals located next to the annular rib.